1. Field of the Invention
The present invention relates to an endoscopic instrument inserted into an operation channel of an endoscopic apparatus.
The present application claims priority to Japanese Patent Application No. 2007-122524 filed May 7, 2007, the content of which is incorporated herein by reference.
2. Background Art
Conventionally known instruments, e.g., needle knives for endoscopic insertion use into body cavity incise mucosa etc. using high-frequency electric current (see Japanese Unexamined Utility Model (Registration) Application Publication No. S61-191012, hereinafter called Patent Document 1). Instruments of this type have an incising section, e.g., an interventional needle knife on a distal end of a wire inserted into an insulative sheath inserted through all endoscope channel. The incising section is capable of freely projecting or retracting relative to the distal end of the sheath by maneuvering a maneuvering member having a proximal end of the wire attached thereon.
Projection length, which is generally short, of the incising section of the aforementioned instrument cannot be adjusted easily. Also, in many cases, the maneuvering amount of the maneuvering member does not correspond to the projecting/retracting amount of a distal end member equally since the endoscope inserted into a body cavity makes complex curves. This enables only two-step adjustment of the incising section, i.e., full projection state and full retracted state into a sheath under present circumstances.
An endoscopic incision instrument proposed for solving the problem has an engagement section having a greater diameter than an inner diameter of a sheath disposed on an electrode or a maneuvering section located in the sheath. This enables fine adjustment of the projection length by means of preload applied when extending or retracting the incising section (see Japanese Unexamined Patent Application, First Publication No. 2004-544, hereinafter called Patent Document 2).
However, adjusting the projection length of the incising section by the incision instrument proposed in Patent Document 2 necessitates observing an image of the distal end picked up by the endoscope distally slantwise. The above method is difficult to reliably obtain desirable projection length since generally the projection length is subject to small pitch, e.g., 0.5 mm etc.
The present invention was conceived in consideration of the aforementioned circumstances, and an object thereof is to provide an endoscopic instrument that can easily and reliably adjust and maintain two or more stepwise projection length of the incising section relative to a sheath.